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Re: [Xen-devel] [PATCH 0/4] HVM Virtual S3

To: "Yu, Ke" <ke.yu@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0/4] HVM Virtual S3
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 17 May 2007 14:06:39 +0100
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Thread-topic: [Xen-devel] [PATCH 0/4] HVM Virtual S3
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On 17/5/07 13:39, "Yu, Ke" <ke.yu@xxxxxxxxx> wrote:

> Virtual S3 is also an important part of host S3, when HVM domain is assigned
> with physical device, e.g. with VT-d introduced. When host S3 begins, HVM
> domain should suspend its physical device,  otherwise the physical device may
> not work after resume. This is the reason why we develop the vritaul S3
> feature: help VT-d HVM domain to do power management. In this case,
> integrating save/resotre with virtual S3 is not necessary,  and it actually
> brings extra overhead.
> To summary, virtual S3 can have two functionality
> - assist HVM to do save/restore
> - assist HVM to do vt-d device power management
> The first item need to call save/restore while the second item do not.

Yes I absolutely agree with all the above. I don't think we want full
save/restore for host S3 at all. We just want to give the domains a little
kick so that they at least resync their clocks, maybe regain DHCP leases,
etc, when the system comes back up.

> So is it possible that we have two code path, and use flags to tell virtual S3
> which path it should go?

I think we'll end up with something like this in the tools, yes. But let's
get the save/restore one plumbed in first. The second case needs integration
with VT-d patches and host S3 patches, which aren't yet in the tree.

> BTW, I did not see current host S3 patches save/restore all domains. Could you
> please elabroate more?

They were posted by your Intel colleague Kevin Tian just a few days ago.

 -- Keir

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